Implement Credentials for Data MVP

[thobson88]

Notes on hackmd: https://hackmd.io/h7FX48jpSOCuKoPmMs61bQ?view

Main steps:

• [x] Create a VC template for a dataset credential (see here)
• [x] Choose a sample dataset
  • e.g. the data.tar from the (recently) most downloaded dataset on huggingface
• [x] Construct a VC for the sample dataset
• [x] Test signing and verification of that VC
• [x] Find a convenient way to share the credential with the dataset ~- e.g. with xattr; note that extended attributes don't affect the hash; link to xattr crate~
• [x] Update the Trustchain CLI to handle signing & verification of credentials for data

[thobson88]

Signing & verifying a credential (already implemented):

trustchain-cli vc sign -f <CREDENTIAL_FILE> --did <DID>
trustchain-cli vc verify -f <CREDENTIAL_FILE>

Signing a dataset (proposed):

trustchain-cli data sign -f <DATASET_FILE> --did <DID>
trustchain-cli data verify -f <DATASET_FILE> -c <CREDENTIAL_FILE>

(other options same as for vc case)

[thobson88]

I've removed the xattr stuff because it's platform-dependent and is a file system feature, so the attributes are not (in general) retained when the file is transferred.

[thobson88]

To try out the updated CLI, checkout the branch:

git checkout 181-credentials4data

Then either install the CLI:

cargo install --path trustchain-cli

and then run the trustchain-cli command as usual.

Or, descend to the trustchain-cli directory:

cd trustchain-cli

and run the binary:

cargo run --bin trustchain-cli